168 REPORT — 1841. 



Messrs. Dumeril and Bibron*, and, in that section, to the genus Platemys : 

 not enough of the skeleton of any individual has yet been obtained to afford 

 a foundation for a specific character. 



Large Emydian from the Kimmej-idge Clay. — In the museum of Sir P. 

 Grey Egerton is preserved the pubic bone of a large Emydian tortoise, ob- 

 tained from Heddington Pits. The bone measures 4^ inches in length, and 

 2 inches 10 lines in the breadth of the symphysial plate. As its specific de- 

 viations, particularly in regard to the length of the sternal process, from the 

 pubis of ordinary Emydians are well marked, it may probably belong to a 

 species of Platemys. 



Footsteps of Emydians in New Red Sandsto7ie. — Among the numerous 

 footsteps of Reptiles impressed upon the sandstone of Stourton Quarries, 

 Cheshire, those of an Emydian Tortoise of moderate size are not uncommon. 



Genus Trionyx. 



Certain British fossils from the secondary formations, referred to Trionyx, 

 have been proved to belong either to another family of Chelonians, or to a di- 

 stinct class of animals. We learn from Dr. Buckland, that the supposed Tri- 

 onyx from the new red sandstone at Caithness (Caithness slate), has been pro- 

 nounced by M. Agassiz to be part of a fish : it is referable to the ganoid genus 

 Coccosteus. 



I have as yet seen no Chelonite from the Wealden freshwater formations 

 that can be confidently affirmed to belong to Trionyx. The specimen de- 

 scribed and figured in the ' Illustrations of the Geology of Sussex,' 4to, p. 60, 

 pi. vi. fig. 8, is the dermal scute of the Crocodilian genus Goniopholis, as Dr. 

 Mantell himself has subsequently recognized : the other portions (pi. vi. figs. 

 1, 3, 5) belong, as already observed, to the Tretosternon punctatum, a species 

 which, like the Goniopholis, is common to the Wealden of Tilgate and the 

 Purbeck limestone. 



Femur from lias at Linksjield. — I have been favoured by Mr. Robertson 

 of Elgin, with the examination of a Chelonian femur, 4f inches in length, 

 from a stratum at Linksfield, in which remains of Plesiosaurus and Hybodus 

 occur ; and this femur, though not identical in form with that of any Trio- 

 nyx with which I could compare it, yet resembles the modifications of the bone 

 in that genus more closely than in Tortoises, Emydians or Turtles. 



Although some of the turtles of the Eocene period, as the Chelone lotigi- 

 ceps, present such modifications of the jaws as seem to have adapted them to 

 habits and food analogous to those of the Trionyx, yet evidences of this 

 genus, to which the destruction of the eggs and young of Crocodiles is more 

 particularly assigned in the Nile and Ganges, are not wanting in certain lo- 

 calities where the London clay appears to have been deposited under circum- 

 stances analogous to those at the termination of equally gigantic rivers. 



Unequivocal portions of a true Trionyx have been obtained from the 

 Eocene clay at Sheppey, and at Bracklesham : they are also associated, as in 

 the Paris basin, with remains of Anoplotherium and Palceotherium in the 

 Eocene lacustrine deposits of the quarries at Benstead in the Isle of Wight. 



Family Chelonidje, Thalassianf family, or Tui'tles. 

 Genus Chelone. 

 Chelone planiceps, nob. — The oldest British geological formation from which 



* Erpetologie, 8vo, 1835, torn. ii. pp. 1/2, 372. 



t "Cheloniens ThaJassites," Dumeril and Bibron, /. c, p. 506. The unfortunate similarity 

 of tlie generic name of the maiine Chelonians, viz. Chelone, with the name of the order, Che- 

 Ionia, renders the term ' thalassian' convenient, in allusion to the peculiarities of the marine 

 species or ' Turtles.' 



